Fine-structure branching ratios and Doppler profiles of Cl(2<i>P</i> <i>j</i>) photofragments from photodissociation of the chlorine molecule near and in the ultraviolet region

Abstract

Photofragment chlorine atoms in the 2Pj states from Cl2 at 266–500 nm are measured by a resonance-enhanced multiphoton ionization technique. The measured branching ratio of [Cl*(2P1/2)]/[Cl(2P3/2)] increases monotonically with dissociation wavelengths from (9.5±1.8)×10−3 at 308 nm to (4.7±0.5)×10−1 at 475 nm. At 375 nm≤λ≤475 nm, Doppler profiles of the chlorine atoms indicate adiabatic formation of two Cl(2P3/2) from the 1Π(1u) state of Cl2 and Cl(2P3/2)+Cl*(2P1/2) from the B 3Π(0+u) state. On the other hand, at a shorter wavelength (308 nm), Cl*(2P1/2) is generated from the 1Π(1u) state through nonadiabatic transitions during the dissociation. The relative contribution of the 1Π(1u)←X 1Σ(0+g) and B 3Π(0+u)←X 1Σ(0+g) transitions in the photoabsorption is estimated from the obtained branching ratios at 375 nm≤λ≤475 nm.